I'll say this quote: "If guns were outlawed, only outlaws would have guns." The criminals already breaking laws would not care whatsoever if they were illegal or not. It wouldn't make any difference to them. Taking away guns from non-criminal people would make them vulnerable and not able to protect themselves which would just make the people with guns insanely powerful and just as powerful as the police.
There is already an abundance of firearms that are illegally owned and operated in the United States, and the ATF has admitted on multiple occasions that it is incapable of enforcing all the official gun laws currently on the books, so it would be futile, and wholly irresponsible to require that the legal gun users surrender their firearms. It would make it harder for some people to protect their homes and lives, while failing to solve the massive problem of illegal firearms.
Taking guns away is downright stupid. If that was a law, I'm sure the criminals would find ways to get guns anyways, and we would be defenseless. Let's take a look at Switzerland. Military personnel can have full auto weapons of duty in their homes, and crime involving weapons like that is very low.